Antistatic films

ABSTRACT

A hydroxyorganosilane composition which upon curing provides a polymer that is an electrical conductor is disclosed. The composition comprises 1 to 95 weight percent of a hydrolyzate of a hydroxyorganosilane and optionally up to 50 weight percent of a silanol-sulfonate compound. When the cured polymer, which has a siloxane backbone, is a film in a composite structure, the resultant article has antistatic properties.

DESCRIPTION TECHNICAL FIELD

The present invention relates to a hydroxyorganosilane composition whichupon curing provides a polymer that is electrically conductive. When thecured polymer is a film in a composite structure, the resultant articlehas antistatic properties. Methods of preparing the conductingcomposition and composite structure are disclosed.

BACKGROUND ART

Many organic materials, especially polymers and polymeric films, displaya decided tendency to acquire an electrostatic charge when handled orprocessed. This results in a number of known practical difficulties, forexample, in manufacturing operations and subsequent uses. The prior arthas dealt with the control of static charges by bleeding them off usingconductive materials as antistatic agents. Varying degrees of successhave been obtained with inorganic metallic foils, vacuum metallizing,and conductive coatings on polymeric substrates.

Polymers having antistatic properties have been prepared by free-radicalor cationic polymerization of certain vinyl monomers. U.S. Pat. No.4,248,750 relates to a linear siloxane with pendant vinyl groups thatcrosslinks by hydrosilation to provide a polymer having both silane-typeand carbon-type linkages in its backbone. W. German OffenlegungsschriftNo. 2,051,832 discloses a vinyl monomer copolymerized with asilanol-containing vinyl monomer, hydrolyzed with sulfuric acid, andthen cured to produce an antistatic polymer having a large proportion ofcarbon to carbon linkages in its backbone.

Also known in the art are polymers having antistatic properties whichhave been prepared by polymerization through a silicon functionality. InU.S. Pat. No. 4,294,950 monomers having silane and epoxide functionalityare subjected to hydrolysis of the silane moieties to provide silanols.Polymerization and curing in the presence of polyvalent carboxylic acidsand curing agents provide polymers having backbone polyester andsiloxane groups.

Antistatic prior art materials frequently suffer from a seriousperformance deficiency; namely, a critical dependence of conductivity onrelative humidity. Prior art materials, other than metal-likeconductors, provide little, if any, static protection below 20 percentrelative humidity. Many such materials impart a greasy feel to thearticle and the antistatic performance can be adversely affected bywashing with solvents. These materials frequently exhibit inadequateabrasion resistance, durability, and transparency. There remains a needin the art for polymeric materials having antistatic properties at verylow relative humidities.

Dilute aqueous solutions of certain terminal monohydroxy-substitutedorganosilanols have been disclosed in U.S. Pat. No. 3,161,611 as usefulfor impregnation of paper, textiles, leather and other materials.Coating compositions comprising these silanols are not described.Aqueous di- or polyhydroxy-substituted organosilanols, with or withoutsilanol-sulfonate compounds, are novel in the art. The cured coatedcompositions of any of the above materials have not been previouslydisclosed.

DISCLOSURE OF THE INVENTION

Briefly, the present invention provides a composition comprising ahydroxyorganosilane, and optionally, a sulfonic acid-substitutedorganosilane, which cures to a transparent, durable, conductive polymerhaving a siloxane backbone and which has antistatic properties even atrelative humidities of 7 percent or lower.

In another aspect, the present invention provides a conductive compositestructure comprising: (1) a suitable substrate coated on at least onesurface with (2) a composition comprising the cured reaction product ofa hydroxyorganosilane and, optionally, a sulfonato-organosiliconcompound. The conductive composite can be optionally overcoated on anyexposed surface with another film. A substrate coated with theconductive film of the present invention is useful to remove or draw-offstatic electric charges, has an electrical conductivity which isrelatively independent of humidity, and can possess both antifoggingcharacteristics and cation exchangeability. The conductive compositestructure, when comprising an overcoated polymeric film having specificproperties can possess additional desirable characteristics, such ashigh abrasion resistance, imageability, or adhesiveness. Surprisingly,such constructions retain superior surface conductivities even thoughthe overcoating film is non-conductive.

In another aspect, the present invention provides conductive polymericcompositions which are prepared by the condensation polymerization ofhydroxy and polyhydroxy group-containing organic monomers fromessentially aqueous solution, preferably using acid catalysts to helppromote polymerization. During the condensation reaction water isremoved from sulfonated or non-sulfonated hydroxyalkyl-substitutedsilanols, siloxanols, or oligomers thereof, or polysiloxanes containingsilanol groups or hydrolyzable protected silanol groups. The use of acidcatalysts in curing the monomers of this invention is desirable evenwhen the monomers contain "built-in" acidic groups such as sulfonic acidgroups. On curing, these monomers form hard, solvent resistant,conductive polymeric films of high dielectric constant which are usefulfor drawing off potential static charges, function relativelyindependently of humidity (surprisingly, even down to a relativehumidity of 7 percent or lower), and may possess antifoggingcharacteristics.

As used in this application:

"hydroxyorganosilane" means any organic group-substituted silane,wherein the organic group is covalently attached to a silicon atomthrough a carbon atom, and wherein the organic group has at least oneattached hydroxy group;

"sulfonato-organosilicon compound", often referred to herein assilanol-sulfonate, means any organic group-substituted silane, whereinthe organic group is covalently attached to a silicon atom through acarbon atom, and wherein the organic group has at least one attachedsulfonic acid group (or its salt form);

"solution" means mixtures and compositions wherein water is present.Such solutions may use water as the only solvent, or they may employcombinations of water with water-miscible organic solvents such asalcohol and acetone. Further, substantial amounts of organic solventsmay be included in the combinations;

"film" means a cured, polymerized organic composition;

"cured" means crosslinked to a three-dimensional structure;

"coating composition" means an uncured organic composition; and

"exhaustive hydrolysis" means a reaction of hydrolyzable groups withwater at low pH, preferably of pH less than 2, to generate ahydroxy-substituted group.

The present invention provides for the preparation and application oflow cost organosilanes which upon curing provide polymers havingexcellent conductivity and abrasion-resistance which extends theirapplications beyond the limits of typical antistatic agents. Thepolymeric compositions described in this invention show excellentdurability in terms of both solvent and abrasion resistance. The curedpolymers of this invention are clear, tintable, and flexible, and theyare easily prepared and applied. Moreover, these materials function notonly as excellent top coatings in antistatic and antifoggingapplications, but they also display conductive properties asundercoatings or sub-layers in composite constructions in a variety ofapplications wherein surface charges need to be electrically grounded ordissipated.

While there is no clear division between conductive and resistive films,it is generally considered that a material having a resistivity ofgreater than 10¹³ ohms per square (ohms/sq) shows insulating properties,while a material having a resistivity of less than 10¹³ ohms/sq exhibitsconductive properties.

The conductive polymeric films of the invention may be self-supportingor they may be formed by coating a composition onto a substrate andcuring this coating to form the conductive polymeric film. Optionally,overcoating compositions can be incorporated in the composite structure.One or more compositions can be overcoated onto either surface of theconductive film-coated substrate and then cured. For example, anoptional overcoating can be a highly abrasion resistant polymeric film,a photographic film, an adhesive layer, a dielectric layer, or a lowadhesion backsize.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a composite structure comprising:

a. a substrate,

b. a cured film on at least one surface of said substrate, said filmcomprising a cured hydroxyorganosilane, and optionally an organicgroup-substituted silane, wherein said organic group is covalentlyattached to a silicon atom through a carbon atom, and wherein saidorganic group has at least one sulfonic acid group, or its salt form,attached thereto, and

c. optionally, a second continuous or discontinuous layer may be adheredon any exposed surface.

Preferably, the curable hydroxyorgaosilane composition of the presentinvention is coated upon a substrate and subjected to in situ energycuring.

The coating composition of the present invention comprises:

1. 1 to 95 weight percent of a silane hydrolyzate derivative of anorganosilane dissolved in 5 to 99 weight percent of an aqueous solvent,said organosilane having the general formula

    R.sup.1 --Si(OR.sup.2).sub.3                               I

wherein R¹ is a hydroxy- or polyhydroxy-substituted organic grouppreferably selected from:

a. alkyl groups having from 2 to 8 carbon atoms and substituted by 1 to7, and preferably 2 to 7, hydroxy groups, with any single carbon atomhaving at most one hydroxy group attached;

b. alkyl groups and cyclic alkyl groups having up to 20 carbon atoms,which carbon chain may be interrupted by one or more oxygen atoms andcontaining at least one, and preferably at least 2, hydroxy group per 8carbon atoms, with any single carbon atom having at most one hydroxygroup attached;

c. aralkyl or alkaryl groups containing 7 to 10 carbon atoms, saidaralkyl or alkaryl group having 1 to 8, and preferably 2 to 8, hydroxygroups, with any single carbon atom having at most one hydroxy groupattached;

d. alkenyl group containing up to 8 carbon atoms and 1 to 5, andpreferably 2 to 5, hydroxy groups, with any single carbon atom having atmost one hydroxy group attached;

e. cyclic or alkyl-substituted cyclic groups having up to 8 carbon atomsand substituted by 1 to 7, and preferably 2 to 7, hydroxy groups, withany single carbon atom having at most one hydroxy group attached; and

f. those precursor groups such as epoxy, ketal, acetal and ester which,on exhaustive hydrolysis, provide the aforementioned hydroxy, andpreferably dihydroxy or polyhydroxyalkyl, groups.

Wherever the term "group" is used in the definition of a term (as inalkyl group versus alkyl), the term connotes the possibility ofsubstitution recognized by the art as not affecting the functionalnature of the chemical term. Where the term "aralkyl or alkaryl group"is used, unsubstituted or substituted phenyl is anticipated, andsubstituent groups include, for example, lower alkyl of 1 to 4 carbonatoms, nitro, halo, cyano, hydroxy, and ether groups, with no more thanone substituent group on any carbon atom of the phenyl group.

R¹ most preferably is a dihydroxy-substituted alkyl group containing 4to 8 carbon atoms whose chain may be interrupted by one or two oxygenatoms or the appropriate hydroxy precursor which on exhaustivehydrolysis gives the most preferred R¹ group; and

R² is selected from (1) hydrogen, and (2) any organic group such thatthe --Si(OR²)₃ moiety is hydrolyzable. For example, useful groupsinclude straight chain or branched alkyl, alkaryl, acyl, or aroyl grouphaving up to 8 carbon atoms which allows hydrolysis of the --Si(OR²)₃moiety to give a silanol hydrolyzate or oligomers thereof. Useful groupsinclude methyl, ethyl, octyl, methoxyethyl, acetyl, phenyl, benzyl, andbenzoyl.

Organosilanes in which R¹ is a dihydroxy-substituted alkyl group is mostpreferred due to the ease of preparation of these materials and theready availability of starting materials.

Examples of organosilanes having the general Formula I above are:##STR1##

2. From 0 up to about 50 weight percent of a sulfonato-organosiliconcompound (referred to hereinafter as silanol-sulfonate) may be added,said silanol-sulfonate compound having the general formula ##STR2##wherein Q is selected from hydroxyl, alkyl groups containing from 1 to 4carbon atoms, and alkoxy groups containing from 1 to 4 carbon atoms;

X is an organic linking group;

Y is any organic or inorganic cation. Preferably Y is selected fromhydrogen, alkali metals (e.g., lithium, sodium, potassium), alkalineearth metals (e.g., magnesium, calcium), transition metals (e.g.,manganese, cobalt, copper, zinc), heavy metals (e.g., lead), organiccations of protonated weak bases having an average molecular weight ofless than about 400 and a pK_(a) of less than about 11 (e.g.,4-aminopyridine, 2-methoxyethylamine, benzylamine,2,4-dimethylimidazole, 3-[2-ethoxy(2-ethoxyethoxy)]propylamine), andorganic cations of strong organic bases having an average molecularweight of less than about 400 and a pK_(a) of greater than about 11[e.g., ⁺ P(CH₂ C₆ H₅)(C₆ H₅)₃, ⁺ N(CH₃)₄, ⁺ N(CH₂ CH₃)₄ ]; mostpreferably Y is hydrogen;

r is equal to the valence of Y; and

n is 1 or 2; with the proviso that the mole ratio of silanol-sulfonateto organosilane is less than 5 to 1.

X is any organic linking group containing up to 10 carbon atoms and notfunctionally involved in the polymerization of the molecule. PreferablyX is selected from alkylene groups having at least two or more methylenegroups, cycloalkylene groups, alkyl-substituted cycloalkylene groups,hydroxy-substituted alkylene groups, hydroxy-substituted mono-oxaalkylene groups, divalent hydrocarbon groups having mono- or poly-oxabackbone substitution, divalent hydrocarbon groups having mono-thiabackbone substitution, divalent hydrocarbon groups having dioxo-thiabackbone substitution, divalent hydrocarbon groups having monooxo-thiabackbone substitution, arylene groups, arylalkylene groups, alkylarylenegroups, substituted alkylarylene groups, and alkylarylalkylene groups.Most preferably, X is selected from alkylene groups having at least twoor more methylene groups or such hydroxy-substituted alkylene groups andhydroxy-substituted mono-oxa alkylene groups having a total of up to 10carbon atoms.

Where a silanol-sulfonate compound is used it is present in the range of0.001 to 50 weight percent.

Organosilanol-sulfonic acids are a preferred class of compounds withinFormula II and are present in the most preferred coating solutions andfilms of the present invention. These compounds have the formula##STR3## wherein Q, X and n are each as described above. Examples oforganosilanol-sulfonic acids of Formula III are

    (HO).sub.3 --Si--X--SO.sub.3.sup.- H.sup.+                 (IIIA) ##STR4## In these formulae, X is as described above and Q' is an alkyl group which contains from 1 to 4 carbon atoms. Representative compounds or oligomers of Formulae III(A-C) include: ##STR5## Of these specific compounds, those of formulae (a), (c), (d) and (i) are preferred, with compound (a) being particularly preferred. Useful starting materials in the preparation of compounds (a) through (i) above are disclosed in U.S. Pat. No. 4,235,638, col. 6, and the starting material of compound (j) is disclosed in U.S. Pat. No. 2,968,643 (Exs. IV and V), both patents being incorporated herein by reference.

The aqueous solutions of the organosilanolsulfonic acids are acidic andthey usually have a pH of less than about 5. Preferably, they have a pHof less than about 3. Most preferably, they have a pH in the range ofabout 0.5-2.5.

Organosilanol-sulfonic acid salts represent another class of compoundswithin Formula II which are useful in either or both the solutions andcured compositions of the present invention. These compounds arewell-known in the art and have the formula ##STR6## wherein X, n and rare each as described above, Q" is selected from hydroxyl and alkylgroups containing from 1 to 4 carbon atoms, and Y is as described aboveexcept Y is not hydrogen. Examples of organosilanol-sulfonic acid saltsof Formula IV are: (a) (HO)₃ Si-CH₂ CH₂ SO₃ ⁻ K⁺, (b) (HO)₂ Si-(CH₂ CH₂SO₃ ⁻ Na⁺)₂, (c) (HO)₃ SiCH₂ CH₂ CH₂ SO₃ ⁻ N⁺ (C₂ H₅)₄, and (d) (HO)₃SiCH₂ CH₂ CH₂ O-CH₂ CH(OH)CH₂ SO₃ ⁻ Ba_(1/2) ⁺².

The aqueous solutions of the organosilanol-sulfonic acid salts areapproximately neutral. Thus, they have a pH in the range of about 5 to9.

Compounds represented by Formulae I, II, III, and IV above may alsoexist as oligomers in aqueous solution and are useful as such in thepresent invention.

Optionally, monomeric or polymeric alkyl-, aryl-, alkaryl-, andaralkyl-sulfonic acids having up to 20 carbon atoms per sulfonic acidgroup (e.g., dodecylbenzenesulfonic acid, benzenesulfonic acid,ethanesulfonic acid, polystyrenesulfonic acid, and methanesulfonic acid)or the salts of such acids may be used. However, they do not normallyprovide the water or solvent durability that is provided by preferredco-reacted silanol-sulfonate materials, i.e., simple sulfonic acids tendto migrate or be leached out of the cured conductive film. However, oncethe conductive polymeric film is overcoated with an abrasion resistantfilm, for example, the conductive polymeric film is relativelyimpervious to the leaching effects of water. Phosphonic acids withstructures similar to those of the sulfonic acids described above arealso useful.

The function of the preferred sulfonic acids is not only to providesulfonate functionality, but also to serve as an acid in promoting thein situ exhaustive hydrolysis of any hydroxyl precursor, as describedabove, to its corresponding alcohol. Such hydrolytic processes may beexothermic and can be monitored by spectroscopic means, as for example,by infrared and nuclear magnetic resonance spectroscopies.

3. Optionally, an Acid Catalyst

Use of an acid catalyst is usually desirable particularly to affordhard, solvent resistant films. Any acid catalyst which speeds up thecuring of the hydroxyorganosilane composition is useful. Useful acidcatalysts include inorganic acids as, for example, sulfuric acid, nitricacid, phosphoric acid, antimony pentafluoride, antimonypentachloridedimethyl methylphosphonate (see U.S. Pat. No. 4,293,675),hexafluoroantimonic acid and such acidic organic materials as, forexample, p-toluenesulfonic acid and other monomeric or polymericsulfonic acids, bis(perfluoromethanesulfonyl)methane (see U.S. Pat. No.2,732,398), higher homologs of such fluorinated sulfonyl methanes (seeU.S. Pat. Nos. 3,281,472, 3,632,843 and 4,049,861),trifluoromethanesulfonic acid and higher perfluorinated homologs (seeU.S. Pat. No. 4,049,861), and photoactivatable initiators such as, forexample, triarylsulfonium hexafluoroantimonate and similar compounds(see U.S. Pat. No. 4,173,476). These catalysts can be present inconcentration ranges from about 1 to about 5 weight percent based on thepercent solids of the total reactive monomers. Hexafluoroantimonic acidhexahydrate is a preferred catalyst.

Substrates useful in the present invention are fibers, sheets and thesurfaces of shaped solid objects. Among the preferred substrates areceramic materials (e.g., glass, fused ceramic sheeting, fibers, andparticulates such as silica), metals (e.g., sheets, fibers, aluminum,iron, silver, chromium, nickel, brass and other metals), metal oxides,thermoplastic resins (e.g., polymethyl methacrylate, polyethyleneterephthalate, cellulose acetate and cellulose acetate butyrate),polycarbonates, polyamides and polyolefins (e.g., polystyrene,polyethylene and polypropylene), acrylic resins, polyvinyl chloride,polysilanes, polysiloxanes, thermoset resins, epoxy resins, paper, woodand natural resins (e.g., rubber, gelatin and silver halide-gelatinemulsions), textiles, foams, laminates, coated articles, and otherorganic and inorganic substrates, any surface of which may benefit froma coated conductive polymeric film.

When the substrate is not naturally adherent with the compositions ofthe present invention, the substrate may be primed first. Many primersare known in the art, and their purpose is to provide a layer to whichthe conductive film more readily adheres than to the original surface ofthe substrate. For example, in the photographic art, primers aregenerally used on the polyethylene terephthalate base to improveadhesion of subsequent layers thereto. A host of commercial primers suchas polyvinylidene chloride, various aliphatic or aromatic urethanes,caprolactones, epoxies, and siloxanes can also find utility as primersfor the films of the invention. The surface of the substrate may itselfbe modified to improve adherence.

Specific substrates used in the present invention include aluminum thatwas previously silicated, brass that was previously treated with anitric acid-ferric chloride solution, polyethylene that was previouslychromic acid etched [see J. R. Rasmussen, E. R. Stedronsky and G. M.Whitesides, J. Amer. Chem. Soc. 99, 4737 (1977)], polypropylene which ischromic acid etched or previously subjected to corona discharge, glasswhich is either first abraded with a scouring powder or etched withchromic acid, and cellulose acetate butyrate which is first treated withcaustic (sodium hydroxide or potassium hydroxide). Polyvinylidenechloride-primed polyethylene terephthalate (commercially available from3M) is a particularly suitable substrate used in this invention.

Additives which serve a given purpose such as viscosity modifiers,hardness modifiers, pigments, fillers, UV absorbers, colorants, levelingagents, and the like, may be added with proper mixing. A leveling agentwhich has been found useful in the practice of the present invention isTriton X-100®, octylphenoxypolyethoxyethanol (Rohm and Haas,Philadelphia, PA). Leveling agents are used in trace to minor amounts,e.g., 0.001 to 1.0 weight percent. Optional additives include numerousorganosilane and organosiloxane monomers and oligomers, for example,methylsilanetriol oligomers, orthosilicates, and those materialsrepresented by the formula: ##STR7## wherein R¹ and R² are defined aboveand R³ is selected from alkyl groups having 1 to 6 carbon atoms orphenyl groups, a is 2 or 3, and b is 1 or 2, with the proviso that (a+b)is equal to 3 or 4. Additives may be added based on the percent solidsof the reactive monomers and may vary from as little as 0.1 to as muchas 20 percent or more. Epoxysilanes are particularly useful additivesfor the preparation of hard and abrasion resistant films. They may beused in amounts in the range of 0.1 to up to 95 weight percent ofreactive monomers.

The pH range of these formulations can be from about 0.5 to about 11,depending upon the selection of components. Since there is a correlationbetween higher conductivity and lower pH, subsequent addition of basicadditives to the preferred acidic formulations is limited so that the pHof the resulting coating formulation remains less than about 5,preferably less than about 3, and most preferably less than about 2.This also encourages a curing rate which is not excessively slow andalso provides hard, solvent resistant films. Solvents may be added toadjust the viscosity of the uncured solution. These compositions areusually, and preferably, used shortly after they are prepared; however,they may be prepared and stored at room temperature or below for severaldays before application.

To prepare the composite structure of the present invention, solutionsof the components of the coating composition, i.e., the organosilanehydrolyzate, the optional silanol-sulfonate and the optional acidcatalyst are simply mixed or blended. This mixture is allowed to standuntil exhaustive hydrolysis, where necessary, is complete. Heating maybe required. The preferred order of addition of ingredients is to addthe silanol-sulfonate to the silane.

The solution is applied to a substrate, which can be in the shape of apolymeric film, or a preformed article made of, for example,polyvinylidene chloride-primed polyethylene terephthalate, by dipping,brushing, spraying, knife coating, bar coating, and painting, or by anyother suitable coating method. A coating method conveniently used inthis invention employs RDS bar coaters (RD Specialties, Webster, NY)which allow the coating of resultant films of specified thicknesses.Cured coating thicknesses of about 0.1-25 microns are particularlyuseful, with a thickness in the range of about 1-10 microns beingpreferred. Where desired, thicker coatings can be applied.

The composition of the present invention coated on a substrate can becured in situ by heat or microwave radiation which causes polymerizationof the coated compositions of the present invention, and will providehard, solvent resistant films provided such films are adequatelydehydrated during the curing process.

The preferred method of curing these coatings is by application of heatwith temperatures ranging from about 60°-120° C.; more preferably thetemperature is in the range of about 80°-100° C. Higher or lowertemperatures can be used. The duration of curing ranges from as short asabout 2 minutes to as long as about 16 hours, with a preferred curingtime of about 30 minutes at 90° C.

It is preferable that both radiation and heat be used to cure thecoating compositions when a triphenylsulfonium hexafluoroantimonate orsimilar photoactivatable material is used, as described in U.S. Pat. No.4,173,476. Neutral coating compositions containing photoactivatablecatalysts have the advantage of longer shelf life than those containingadded acidic materials. Any suitable source which emits actinicradiation and preferably ultraviolet radiation may be used to activatethese catalysts in the practice of this invention. Suitable sources aremercury arcs, carbon arcs, low-, medium-, and high-pressure mercurylamps, plasma arcs, ultraviolet light emitting diodes, and ultravioletemitting lasers. Typical cure conditions with such ultraviolet lightsources involve the conveying, or repeated conveying, of an overcoatedsubstrate several centimeters from the source of a 200 watt per 2.54 cm(1 inch) medium-pressure mercury vapor lamp preferably in areflectorized housing for maximum radiation exposure with, optionally, aconveyor moving at a suitable speed, for example, 15 meters/minute (50feet per minute).

Another convenient means of preparing cured polymeric compositions whichincorporate the optional silanol-sulfonate salt of Formula IV involvesthe preparation of cured films comprising the silanol-sulfonic acidsdescribed above and subsequently replacing the proton of the sulfonicacid groups in the cured films by a desired cation. One method involvesthe ion-exchanging of the desired cation into a film by immersion of thecured film into a solution of a neutral or basic salt of the desiredcation. Another method, for example, is to form protonated weak bases asthe cationic species by reaction of the sulfonic acid groups in thecured film with a weak base having a pK_(a) of less than about 11.Again, this may be accomplished by immersion of a cured film into asolution of the weak base. Conversely, by ion-exchange methods,silanol-sulfonate salt-containing films may be converted tosilanol-sulfonic acid-containing films by immersion in protonic acidsolution. Furthermore, the cations of the silanol-sulfonatesalt-containing films may be interchanged.

It may be desirable to modify the surface of the cured polymericconductive film by lowering its coefficient of friction and therebyimparting certain desirable handling qualities. This can be accomplishedby applying, for example, fluorocarbons, release agents, or antiblockingagents to the film by methods such as those taught in U.S. Pat. No.4,293,606.

Surprisingly, overcoating a first cured conductive film of thisinvention with another compatible film which itself is not conductiveprovides novel composite films of excellent conductivity. The firstcured conductive film of the present invention may also be overcoatedwith a second similar or identical film within the present invention toafford a conductive composite structure having additional desirableproperties, such as abrasion resistance. The second coating formulationor top coating may be selected so as to provide different conductive orother properties in the cured top layer.

Polymeric overcoatings which may be useful can be derived from a varietyof silane monomers and their hydrolyzates (or their respective oligomersor polymeric forms, alone or in combination). Typical examples include:##STR8##

Methods of coating and the subsequent acid catalyzed curing of thesesilane materials to produce cured siloxane films are described in theart. They may be applied from organic solvents or water and may bemodified by the incorporation of various additives such as viscositymodifiers, pigments, fillers, UV absorbers, colorants, leveling agentsand the like.

The coating and overcoating compositions may be applied to a substrateor to a previously prepared conductive polymeric film coated substrateby dipping, brushing, spraying, knife coating, bar coating, painting, orby any other suitable coating method. The coating method convenientlyused in this invention employs RDS bar coaters (RD Specialties, Webster,NY) which allows for the coating of compositions of specifiedthicknesses. The coating thickness of the overcoating compositiondepends on the use of the desired composite film. The practical upperlimit of thickness of the overcoated film depends on the nature of itsconstruction and requires that the resultant composite structure remainsintact after curing.

Curing of the overcoating composition can be accomplished in situ byemploying any energy source appropriate to the specific monomer ormonomers present.

It has been found, surprisingly, that when, for example, apolyvinylidene chloride-primed polyethylene terephthalate substratehaving a conductive polymeric film thereon has an overcoated abrasionresistant polymeric film derived from acid catalyzed curing ofgamma-glycidoxypropyltrimethoxysilane (see Example I below), theresultant composite polymeric film still exhibits good conductivity. Ithas been found, further, that the conductivity of such composites isessentially independent of the thickness of the abrasion-resistantovercoated polymeric film, within practical coating capabilities.Furthermore, the abrasion-resistance of these composite films isexcellent, as indicated by abrasion-resistance haze tests.

Additional overcoatings which may be employed in the practice of thisinvention include numerous surface-modifying siloxane coatings, forexample, release coatings, adhesives, and protective coatings which arewell documented in the art. See, for example, U.S. Pat. Nos. 4,049,861,4,225,631, 4,239,798 and 4,223,121 which relate to abrasion resistantcoatings, and U.S. Pat. No. 3,986,997 which discloses pigment-freecoating compositions. U.S. Pat. No. 4,239,798 describes a siliconecoated polycarbonate article and U.S. Pat. No. 4,101,513 discloses acatalyst for condensation of hydrolyzable silanes and storage stablecompositions thereof. U.S. Pat. No. 4,294,950 relates to a coatingcomposition comprising hydrolyzates from silane compounds.

Many of the characteristics of these polymeric films combine to providematerials with unique and useful properties. During normal use, thesefilms may come in contact with water or abrasive materials or both. Thefilms of this invention show excellent durability with respect to waterwashing or abrading with steel wool. In most instances, the abrasionresistance is superior to that of the uncoated substrate. In compositefilms, wherein the top layer is a cured siloxane abrasion resistantlayer, the hardness may be such that the conductive cured coatings arescratched with steel wool only with difficulty. A quantitative measureof this surface hardness is a film's resistance to abrasion by fallingsand.

Conductivity of the films is readily apparent in their excellentantistatic properties. Surface charges cannot only damage electricalcomponents, but also may attract contaminants such as dust and smokeparticles. When buffed with a tissue, for example, the surfaces of filmsof this invention do not attract small pieces of tissue, paper,cigarette ashes or polystyrene, even down to very low humidities. Staticdecay times (as shown in examples below) illustrate the reluctance offilms to develop or maintain static charges.

Films particularly useful are those having silanol-sulfonates orsulfonato functional organic compounds since they resist fogging. Forexample, such films, when breathed on, resist fogging, even if they areinitially cooled by refrigeration.

The ion exchange characteristics of those polymeric films containing thesilanol-sulfonato component allow easy, rapid tinting, even at roomtemperature. By simple ion exchange of the sulfonato groups with theappropriate cationic dye, such films may be selectively colored toalmost any optical density by immersion of the cured coating into asolution of the dye.

The cured conductive compositions of the present invention are useful ascoatings in composite structures as well as self-supporting curedconductive films. The cured compositions dissipate charges, provideconductive surfaces in imaging technology, serve as a ground plane, mayprevent fogging, and may exchange and bind ions. They are useful withany compatible film or material which might benefit from the use of aconductive sub- or under-layer to dissipate or transport electroniccharge. Examples of such films or materials are adhesives, gelatins,photoemulsions, photoconductive materials and dielectric materials.

Evaluation of various physical properties of the cured compositions ofthe present invention were made. In the evaluation of surfaceresistivity, razor blades were used as flexible electrodes and madeexcellent contact with the polymeric films. The blades were connected toan insulating polymer platform and were attached by use of spring loadedclamps to insure intimate contact with the substrate surface. Theconfiguration was such that the edges of the blades were diametricallyopposed and, thus, described a square-shaped area of approximately 16cm². Electrical contact was made by attachment with coaxial cable from aKeithley 600A electrometer (Keithley Instruments, Inc., Cleveland, OH)to the metallic spring clamps holding the blades.

Conductivity measurements are sometimes made at ambient relativehumidity. To demonstrate the superior performance of the films of thisinvention under adverse conditions, they were often evaluated at lowrelative humidity. The electrodes of the electrometer and the samplewere kept in an enclosed chamber which had therein a material (seeexamples of useful materials in "Lange's Handbook of Chemistry", J. A.Dean, Editor, McGraw-Hill Publishers, New York (1973) 11th Edition, page10-79) which provided a specified relative humidity at a giventemperature under the equilibrium conditions of a closed vessel.

In the static decay evaluation, a sample of the film was charged up to5000 volts, grounded, and the time it took to discharge to 500 volts,was measured. Military specifications (MIL-B-81705) presently accept forstatic protection any film that exhibits a static decay time of twoseconds or less.

The abrasion resistance of polymeric films was measured by the film'sresistance to abrasion by falling sand. One liter of sand 20 to 30 mesh,ASTM Designation C190-77, (Ottawa Silica Co., Ottawa, IL) was droppedthrough an abrasion tester instrument and the falling sand was allowedto impinge onto a film surface whose haze or light transmittingproperties were measured before and after abrasion with sand using aGardner Hazemeter as described in ASTM Method D1003-61 (1977).

Objects and advantages of this invention are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this invention. Parts andpercentages are by weight unless otherwise indicated, and temperaturesare in degrees centigrade. In the following examples, compositions thatlead to conductive polymeric films were applied to substrates using anRDS Bar Coater No. 14, and overcoatings of abrasion resistantcompositions were applied to conductive polymeric film-coated substratesusing an RDS Bar Coater No. 8 (commercially available from RDSpecialties, Webster, NY) unless indicated otherwise. All resistancemeasurements were made with a Keithley Instruments 600A electrometer(Keithley Instruments, Inc., Cleveland, OH). All resistivities aresurface resistivities unless otherwise stated and are given forequilibrated samples at the relative humidity specified.

EXAMPLE 1

Conductive polymeric films were evaluated for surface resistivity (orconductivity) using ASTM Method D257-78 as the model, and for staticdecay using Federal Test Method Standard No. 101, Test Method No. 4046as the model. The polymeric films were prepared from a coatingformulation comprising a mixture of a hydrolyzate solution ofgamma-glycidoxypropyltrimethoxysilane (which solution is hereinafterreferred to as A), with a silanol-sulfonic acid solution derived fromgamma-glycidoxypropyltrimethoxysilane (which solution is hereinafterreferred to as B) wherein the ratio of the two components of thismixture were varied as is indicated in samples 1-5 of Table I.

The hydrolyzate solution, A, of gamma-glycidoxypropyltrimethoxysilanewas prepared by agitation of a mixture of 20 g of this monomer with 10 gof water for about 90 minutes at ambient temperature.

Solution B, the silanol-sulfonic acid solution derived fromgamma-glycidoxypropyltrimethoxysilane, was prepared by slowly adding asolution of 29.5 g of gamma-glycidoxypropyltrimethoxysilane in 14.75 gof water to a solution of 15.75 g of sodium sulfite and 40 g of water.The mixture was stirred and reacted at 50° C. for 16 hours. The pH ofthe resulting reaction mixture was 12.8. The solution was passed throughan excess of the acid form of Amberlite®IR-120 (ion exchange resin, Rohmand Haas Company, Philadelphia, PA). This provided a solution having apH of less than 1. The solution was adjusted to 23 percent solids byweight by addition of water.

In a typical sample formulation, 3 g of A was combined with 1.5 g of Band the resulting solution was allowed to stand at room temperatureuntil any exotherm subsided (about 10-15 minutes, see below). To thissolution was added 2 ml of methanol, a few drops of a 10 percentsolution of Triton X-100, and 40 mg (1-2 percent by weight) ofhexafluoroantimonic acid hexahydrate. This formulation was coated onpolyvinylidene chloride-primed polyethylene terephthalate using a No. 14RDS Bar Coater. The resultant coating was then cured at 90° C. for atleast 30 minutes to give the polymeric film.

The cationic methylene blue dye absorbance evaluation utilized a piece(1 cm×1 cm×about 7 microns thick) of polymeric composite film, whosecomposition is described below. The film sample was immersed in 0.01Maqueous methylene blue (as the chloride) for 15, 30, or 60 seconds, thenrinsed with distilled water, and placed in a Beckman DBspectrophotometer where the absorbance was measured at a wavelength of655 nanometers (nm). A higher absorbance indicates the presence of alarger number of sulfonate groups which bind the methylene blue.

TABLE I gives composition, resistivity, methylene blue absorbance, andstatic decay data for samples 1 to 5.

                                      TABLE I                                     __________________________________________________________________________    Studies of Polymeric Films Derived from Glycidoxypropyltrimethoxysilane       Silane-containing materials                                                                              Methylene blue                                                                            Static decay.sup.c (sec)               Sample                                                                            A   B   Wt. Ratio                                                                           Resistivity.sup.a                                                                      absorbance.sup.b                                                                              Stored                             No. Wt. (g)                                                                           Wt. (g)                                                                           A/B   (ohms/square)                                                                          15 sec.                                                                           30 sec.                                                                           60 sec.                                                                           Initial                                                                           (11 days)                          __________________________________________________________________________     1.sup.d                                                                          3.0 0.5 6     greater than 10.sup.13                                                                 0.05                                                                              0.05                                                                              0.06                                                                              0.24                                                                              0.35                               2   3.0 1.0 3     10.sup.9e                                                                              0.24                                                                              0.30                                                                              0.40                                                                              0.04                                                                              0.06                               3   3.0 1.5 2     10.sup.8 0.99                                                                              1.28                                                                              1.67                                                                              0.06                                                                              0.05                               4   3.0 2.0 1.5   10.sup.8 1.31                                                                              1.64                                                                              2.03                                                                              0.05                                                                              0.04                               5   3.0 3.0 1     10.sup.8 1.45                                                                              1.83                                                                              2.16                                                                              0.05                                                                              0.04                               __________________________________________________________________________     .sup.a measured at relative humidity of 28%; control polyester film had a     resistivity greater than 10.sup.14 ohms/square                                .sup.b control films prior to exposure to methylene blue had an absorbanc     of 0.05 at 655 nm                                                             .sup.c film stored and tested at 7% relative humidity; static decay time      of control polyester substrate was too long for practical measurements        (longer than minutes)                                                         .sup.d when the coating solution was heated for 1 hour at 60° C.,      ensuring exhaustive hydrolysis, conductivity of the cured film was 4.3        × 10.sup.9 ohm/square at 25 percent relative humidity                   .sup.e at 25° C., this material had a dielectric constant of 95 an     a volume resistivity of 1.3 × 10.sup.9 ohmcm at 24° C. and 1     volts; exhaustive hydrolysis of epoxide by reaction of component A with B     was indicated by NMR spectroscopy                                        

The flexible, hard, transparent films of the invention possessedexcellent antifogging and antistatic properties and readily exchangedcationic material. Evolution of heat (exotherm) was usually noted whenepoxy-containing compounds such as gamma-glycidoxypropyltrimethoxysilaneand sulfonic acids were combined in these coating formulations andexternal heat was not required. It was found that if this exotherm wasmoderated by cooling with an ice bath, for example, and this coatingformulation was then cured, the resultant films were less conductive andexhibited higher abrasion resistance than those films prepared fromcoating formulations whose exotherms were not moderated.

The data of Table I show:

(1) a range of silanol-sulfonic acid concentrations are useful inproducing conductive films;

(2) increased amounts of sulfonate in the films allow for increase inconductivity and for an increase in ion-exchange capacity;

(3) the static decay performance of the films is not affected by storageunder dehydrating conditions; and

(4) exhaustive hydrolysis is necessary to generate films of low surfaceresistivity and may be promoted by heating if there is no spontaneousexotherm upon combination of A and B (see sample 1, footnote "d").

EXAMPLE 2

The conductivities of polymeric films having varying amounts ofhydroxyorganosilane monomer components were compared.

The exhaustive hydrolysis product ofgamma-glycidoxypropyltrimethoxysilane[gamma-(beta,gamma-dihydroxypropoxy)-propylsilanetriol] was prepared byone day room temperature stirring of a mixture of 60 ml of 1 percentaqueous sulfuric acid with 40 g of gamma-glycidoxypropyltrimethoxysilane(A-187, Union Carbide, New York, NY). Conventional organic functionalgroup tests for epoxide and diol groups were consistent with theexpected structures. The pH of this solution was raised to about 6 bythe addition of calcium carbonate, followed by filtration throughdiatomaceous earth. The resulting clear filtrate was 22 percent diol(solids) and was used in samples 6-10 of TABLE II below.

Coating formulations were prepared according to the formulations inTABLE II by adding to the requisite amount of dihydroxyorganosilanolsolution prepared above, the corresponding amount of A (EXAMPLE 1),water, a few drops of a 10 percent solution of Triton X-100, and a fewdrops of hexafluoroantimonic acid hexahydrate as the acid catalyst. Toinsure that there was no appreciable hydrolysis of the epoxy function ofthe epoxy functional silane to its diol derivative, the acid catalystwas added immediately prior to coating the resultant formulation ontopolyvinylidene chloride-primed polyethylene terephthalate. The coatingwas cured at 90° for 30 minutes.

                  TABLE II                                                        ______________________________________                                        Resistivity of Films from Diol- and Epoxy-Containing Monomers                 Sam- Diol           Water Approximate                                                                            Surface Resistivity                        ple  wt.    A       added mole ratio                                                                             of polymeric film                          no.  (g)    wt. (g) (g)   diol/epoxy                                                                             (ohms/square).sup.a                        ______________________________________                                        6    4.5    0       0              1.6 × 10.sup.9.sup.                  7    4      0.18    0.32  6.8      5 × 10.sup.9                         8    3      0.57    1     1.8      6 × 10.sup.10                        9    2      0.84    1.7   0.7      5 × 10.sup.12                        10.sup.b                                                                           0      1.5     3     0        greater than 10.sup.13                     ______________________________________                                         .sup.a resistivity measured at 32 percent relative humidity (R.H.)            .sup.b control                                                           

The data of TABLE II show that if the epoxide function ofglycidoxypropyltrimethoxysilane is first converted to the diolderivative followed by silane polymerization during curing, theresultant polymeric film exhibits good conductivity (sample 6). Bycontrast, if the epoxide function of this monomer is not allowed to formthe diol, the cured film (control) shows poor conductivity (sample 10).These experiments clearly illustrate that hydroxyalkyl functionality isimportant in imparting good conductivity to the cured film. Furthermore,the desired conductivity of the conductive polymeric film can bedictated by choosing the proper ratio of diol derivative to epoxidecontaining silane (samples 6-9). In sum, increasing the concentration ofhydroxyorganosilane monomer within the conductive polymeric film resultsin an increase in the conductivity of that film.

EXAMPLE 3

The preparation and use of gamma-hydroxypropylsilanetriol as aconductive polymeric film is shown.

Sodium methoxide solution was prepared by adding 2.3 g of metallicsodium to 100 ml of anhydrous methanol. To the room temperature solutionwas added 22.2 g of gamma-acetoxypropyltrimethoxysilane and theresultant mixture was stirred at room temperature for 22 hours and thenconcentrated to a small volume under reduced pressure. To the residuewas added 50 ml of water and the product was stirred for three hours atroom temperature. This solution was neutralized by ion exchange bypassage through a column of Amberlite IR 120 (in the acid form) toafford a solution of gamma-hydroxypropolysilanetriol at about 7% solids,whose volume was reduced (by concentration under reduced pressure usinga rotary vacuum evaporator) to afford a solution which was about 21%solids. This solution, 5 g, was combined with Triton X-100 andhexafluoroantimonic acid hexahydrate as described in EXAMPLE 1. Theresultant formulation was coated (RDS Bar Coater No. 24) ontopolyvinylidene chloride-primed polyethylene terephthalate substrate andcured at 90° C. for 30 minutes . The cured polymeric film had a surfaceresistivity of 1.5×10¹⁰ ohms/square at 22 percent relative humidity.Note that films prepared from gamma-acetoxypropyltrimethoxysilanewithout prior exhaustive hydrolysis of the acetoxy function are notconductive.

EXAMPLE 4

This example is a study of the correlation between pH and surfaceresistivity.

The acidic solution of the exhaustive hydrolysis product ofgamma-glycidoxypropyltrimethoxysilane (described in EXAMPLE 2 above) wastitrated to pH values between 1.5 and 11.0 with barium hydroxide. Thesediol solutions were coated, cured and the surface resistivities of theresulting films were measured at 25 percent relative humidity. Resultsshowed that film derived from diol solutions of pH 5.0 and above hadsurface resistivities of about 10¹¹ ohms/square, while films derivedfrom diol solutions of lower pH exhibited better conductivities. Forexample, the cured film derived from the diol solution of pH 1.5 had asurface resistivity of 4.8×10⁸ ohms/square and the cured film derivedfrom the diol solution of pH 3.0 had a surface resistivity of 1.4×10¹⁰ohms/square.

EXAMPLE 5

Samples were prepared using essentially the formulations of EXAMPLE 1,except that 0.1 percent by weight of a silica filler (Syloid®308,Davison Chemical Co.) was added to the formulations and coated atdifferent thicknesses using RDS Bar Coater Nos. 3, 8, and 14.Resistivity data showed that the electrical behavior of filler andnon-filler containing polymeric films of different thicknesses wasessentially the same.

EXAMPLE 6

The static decay of portions of film sample 3 of EXAMPLE 1 above wasmeasured and compared with that of a commercial film. The static decaytime (in seconds) of the sample was determined by charging the sample to5000 volts and measuring the time in seconds to decay to 500 volts andthe results are tabulated in Table III.

                  TABLE III                                                       ______________________________________                                        Static Discharge Properties of Films                                          Percent relative                                                                            Static decay (in sec.).sup.a of stored samples                  Sample                                                                              humidity of Initial 1    2     3     1                                  no.   films at 24° C.                                                                    testing week weeks weeks month                              ______________________________________                                        11.sup.b                                                                             7          0.17    0.32 0.75  0.86  0.86                               12.sup.c                                                                             7          0.04    0.04 0.03  0.03  0.04                               13.sup.b                                                                            20          0.13    0.23 1.1   3.2   5.7                                14.sup.c                                                                            20          0.04    0.04 0.04  0.04  0.04                               15.sup.b                                                                            50          0.14    0.22 2.0   16.7  25.2                               16.sup.c                                                                            50          0.04    0.04 0.04  0.05  0.05                               17.sup.b                                                                            75          0.11    0.17 1.54  6.0   11.9                               18.sup.c                                                                            75          0.05    0.04 0.04  0.05  0.04                               19.sup.b                                                                            Saturated   0.18    0.85 12.3  43.0  19.7                               20.sup.c                                                                            Saturated   0.05    0.04 0.05  0.05  0.06                               ______________________________________                                         .sup.a measured at 7% relative humidity, 24° C.                        .sup.b control is Richmond film RCAS 1200 (Richmond Corporation, Redlands     CA)                                                                           .sup.c present invention film                                            

The data of TABLE III show that the conductive polymeric films of thepresent invention maintain their static decay properties and outperforma state of the art material.

EXAMPLE 7

Polymeric films were prepared identical to sample 2 of EXAMPLE 1, exceptthat catalytic amounts (i.e., 2 to 3 weight percent of the silane) ofthe following acid catalysts were included:

(1) hexafluoroantimonic acid hexahydrate

(2) (CF₃ SO₂)₂ CHC₆ H₅ (disclosed in U.S. Pat. No. 4,049,861)

(3) trifluoromethanesulfonic acid The formulations were evaluated, afterheat curing, as to surface resistivity and static decay by methodsdescribed above. The data show that the conductive polymeric films ofthe present invention have excellent surface conductivity and exhibitexcellent static decay independent of the acid catalyst used in thefilms' construction.

A photoactivatable initiator was used as an acid catalyst in a filmprepared as in EXAMPLE 2 but having 1 percent by weight oftriphenylsulfonium hexafluoroantimonate (U.S. Pat. No. 4,173,476) addedto 2 g of 22 percent (in water) hydrolyzed diol,gamma-(beta,gamma-dihydroxypropoxy)propylsilanetriol, containing 1 ml ofisopropyl alcohol with 0.5 percent Triton X-100. This formulation wascoated (RDS Bar Coater No. 14) onto polyvinylidene chloride-primedpolyethylene terephthalate substrate and cured for one minute with amedium-pressure Hanovia ultraviolet lamp (Hanovia Lamp Division,Canrad-Hanovia, Inc., Newark, NJ). The resulting tack-free compositeexhibited a surface resistivity of 5.8×10⁸ ohms/square at 58 percentrelative humidity and 1.5×10¹⁰ ohms/square at 7 percent relativehumidity. This tack-free composite could be thermally cured thereafterto improve film hardness if desired.

EXAMPLE 8

Different silanol-sulfonic acids were used with A (see EXAMPLE 1) togive coatings according to the following procedure.

A coating formulation was prepared according to the method of EXAMPLE 1by mixing 3 g of A with 1 g of selected silanol-sulfonic acid asindicated in Table VI. The silane was used at 67 percent solids and thesilanolsulfonic acid was used at 23 percent solids. After the exothermhad subsided, Triton X-100 and hexafluoroantimonic acid hexahydrate wereadded as in EXAMPLE 1 and the well-mixed coating formulation was coatedwith an RDS Bar Coater No. 14 onto primed polyethylene terephthalatesubstrate. The coating was cured to a hard polymeric conductive film byheating in an oven at 90° C. for 30 minutes. Resistivities of theresultant films (samples 21 to 26) were measured at 9 percent relativehumidity and the results are summarized in Table IV.

                                      TABLE IV                                    __________________________________________________________________________    Resistivity of Films Using Various Silanol-Sulfonic Acids                                                  Film                                             Sample                       surface resistivity                              no. Silane chemical structure                                                                         Source.sup.a                                                                       (ohms/square)                                    __________________________________________________________________________    21                                                                                 ##STR9##           Ex. 1, 2                                                                           3.0 × 10.sup.10                            22                                                                                 ##STR10##          Ex. 7                                                                              2.6 × 10.sup.9                             23                                                                                 ##STR11##          Ex. 9                                                                              2.4 × 10.sup.11                            24  HO.sub.3 SCH.sub.2 CH.sub.2 Si(OH).sub.3                                                          Ex. 3                                                                              7.5 × 10.sup.9                             25  HO.sub.3 SCH.sub.2 CH.sub.2 CH.sub.2 Si(OH).sub.3                                                 Ex. 5                                                                              4.7 × 10.sup.10                            26  HO.sub.3 SCH.sub.2 CH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 CH.sub.2              Si(OH).sub.3        Ex. 6                                                                              8.0 × 10.sup.12                            __________________________________________________________________________     .sup.a example numbers in this column refer to that example in the U. S.      Pat. No. 4,235,638                                                            .sup.b represents a control; prepared as described in Example 1          

The data of TABLE IV show that a variety of silanol-sulfonic acids maybe used to prepare conductive films of the present invention.

EXAMPLE 9

Films prepared as in EXAMPLE 1 but having 3 g of A reacted with organicsulfonic acids (listed below) were evaluated as to resistivity, thenrinsed with about 100 ml of deionized water, which was applied as a finestream onto the film's surface, air dried, and again evaluated as toresistivity. The results indicate that coating and curing offormulations containing organic sulfonic acids as additives producedpolymeric conductive films of acceptable resistivity. However, whenthese films were contacted with water, the films exhibited lowerconductivity. These noncopolymerizable organic sulfonic acid additivesexhibited solvent sensitivity due to their water leachability from, andmobility in, the resultant polymeric films. In contrast, the coreactedsilanol-sulfonic acid-containing films exhibit excellent solventresistance.

The organic sulfonic acids used were ##STR12##

EXAMPLE 10

Samples 27 to 40 illustrate the use of different silanol-sulfonate saltsas components in formulations to give polymeric conductive films.

A coating formulation was prepared according to the method of EXAMPLE 1by mixing 3 g of A with 1 g of B. After the resultant exotherm hadsubsided, the acidic solution (pH about 1) was diluted with 2 ml ofwater (samples 33 to 39) or not diluted (samples 27 to 32, and 40) andtitrated with a base whose cation is indicated in Table V. In theseexamples, a strong base was used and the salt-forming titration wasstopped when the pH was between 4.0 and 4.5. To 4 g of the resultingsolution was added 2 ml of methanol (samples 27 to 32, and 40) or nomethanol was added (samples 33 to 39), 3 drops of 10 percent TritonX-100 in water, and 3 drops of hexafluoroantimonic acid hexahydrate. Thecoating formulation was coated onto polyvinylidene chloride-primedpolyethylene terephthalate substrate using an RDS Bar Coater No. 14, andthe coating was cured in an oven at 90° for 30 minutes. The results areshown in TABLE V.

                  TABLE V                                                         ______________________________________                                        Resistivity of Films Containing Various Silanol-Sulfonate Salts                                        Surface Resistivity                                  Sample                   (ohms/square)                                        no.   Cation.sup.a    pH.sup.b                                                                             9% R.H. 58% R.H.                                 ______________________________________                                        27    (HOCH.sub.2 CH.sub.2).sub.4 N.sup.+a1                                                         5.3    1.4 × 10.sup.10                                                                 7.8 × 10.sup.7                     28    (C.sub.6 H.sub.5 CH.sub.2)(CH.sub.3).sub.3 N.sup.+a2                                          5.3    6.6 × 10.sup.8                                                                  1.0 × 10.sup.8                     29    (CH.sub.3).sub.4 N.sup.+a3                                                                    5.0    2.5 × 10.sup.10                                                                 1.2 × 10.sup.8                     30    (n-C.sub.4 H.sub.9).sub.4 N.sup.+a4                                                           5.3    1.8 × 10.sup.10                                                                 2.0 × 10.sup.8                     31    Na.sup.+a5      5.3    7.0 × 10.sup.9                                                                  8.6 × 10.sup.7                     32    Ba.sup.+a6      5.0    1.2 × 10.sup.11                                                                 7.6 × 10.sup.8                     33    Mg.sup.++a7     5.0    4.1 × 10.sup.10                                                                 2.8 × 10.sup.8c                    34    Zn.sup.++a8     5.0    5.0 × 10.sup.10                                                                 4.3 × 10.sup.8c                    35    Ni.sup.++a9     5.5    1.0 × 10.sup.11                                                                 8.8 × 10.sup.8c                    36    Co.sup.++a10    4.0    4.4 × 10.sup.10                                                                 4.8 × 10.sup.8c                    37    Cu.sup.++a11    4.5    3.0 × 10.sup.10                                                                 2.8 × 10.sup.8c                    38    Pb.sup.++a12    4.0    8.4 × 10.sup.9                                                                  1.0 × 10.sup.8c                    39    Cd.sup.++a13    4.3    2.8 × 10.sup.10                                                                 2.4 × 10.sup.8c                    .sup. 40.sup.d                                                                      H.sup.+         1.0    1.3 × 10.sup.9                                                                  4.7 × 10.sup.8                     ______________________________________                                         .sup.a acidic solution titrated with the following bases:                     .sup.a1 90 percent (HOCH.sub.2 CH.sub.2).sub.4 N.sup.+ OH.sup.-  in water     (RSA Corp., Ardsley, NY)                                                      .sup.a2 40 percent (C.sub.6 H.sub.5 CH.sub.2)(CH.sub.3).sub.3 N.sup.+         OH.sup.-  in methanol (Aldrich Chemical Co., Milwaukee, WI)                   .sup.a3 20 percent (CH.sub.3).sub.4 N.sup.+ OH.sup.-  in methanol (Aldric     Chemical Co.)                                                                 .sup.a4 25 percent (nC.sub.4 H.sub.9).sub.4 N.sup.+ OH.sup.-  in methanol     (Eastman, Rochester, NY)                                                      .sup.a5 25 percent sodium hydroxide in water                                  .sup.a6 saturated barium hydroxide in water                                   .sup.a7 solid magnesium hydroxide                                             .sup.a8 solid zinc carbonate                                                  .sup.a9 solid nickel carbonate                                                .sup.a10 solid cobalt carbonate                                               .sup.a11 solid copper carbonate                                               .sup.a12 solid lead carbonate                                                 .sup.a13 solid cadmium hydroxide                                              .sup.b pH measured after titration and prior to addition of surfactant an     acid catalyst                                                                 .sup.c measured at 53 percent relative humidity                               .sup.d control                                                           

The data show that a variety of silanol-sulfonate salts may be used toproduce conductive polymeric films.

EXAMPLE 11

An organosilane-phosphonic acid was prepared according to the procedureof G. H. Barnes and M. P. David, J. Org. Chem., 25, 1191 (1960).Hydrolysis of 1 g of dimethyl triethoxysilylethylphosphonate in 5 g ofrefluxing concentrated HCl for 23 hours affords, after evaporation ofsolvent, the solid siloxane phosphonic acid.

A coating solution was prepared by combining 1.0 g of a 20% aqueoussolution of the organosilane-phosphonic acid with 2.0 g of a 10% aqueoussolution of [gamma-(beta, gamma-dihydroxypropoxy)-propylsilanetriol] ofExample 2.

A cured film on polyvinylidene chloride-primed polyethyleneterephthalate was prepared according to the procedure of EXAMPLE 1.

The film was flexible, hard, transparent, antifogging, andcation-exchangeable. Surface resistivity of the cured film was 3.8×10¹⁰ohms/square at 12% relative humidity.

The results show that silane phosphonates are also useful in thepractice of this invention.

EXAMPLE 12

Cured films coated on polyvinylidene chloride-primed polyethyleneterephthalate, prepared as described in EXAMPLE 4, were subjected tocation exchange (cations used were Na⁺, Ag⁺, Mg⁺², Cu⁺², Mn⁺², Fe⁺³,Cr⁺³, methylene blue cation, C₆ H₅ CH₂ (C₆ H₅)₃ P⁺, C₆ H₅ CH₂ (C₂ H₅)₃N⁺, (n--C₄ H₉)₄ N⁺, and (NH₂)₂ C═NH₂ ⁺. Cations used were exchanged intothe silanol-sulfonic acid-containing films and the resulting filmsshowed excellent conductivity.

EXAMPLE 13

A pressure sensitive, conductive film-containing tape which can bedispensed according to length to overcome a problem of chargegeneration, was prepared.

The coating formulation of sample 2, TABLE I above, was preparedaccording to the method of EXAMPLE 1. This formulation was coated ontopolyvinylidene chloride-primed polyethylene terephthalate substrate andthe coating was cured to yield a conductive polymeric film. The top,conductive surface of this film was overcoated (using a RDS Bar CoaterNo. 3) with a release coating composition such as a low adhesionbacksize.

The pressure sensitive adhesive (such as a water-based acrylate) wasnext applied (using RDS Bar Coater No. 8) to the remaining, uncoated,suitably primed surface of the substrate. The resultant conductivecomposite tape may be affixed, e.g., by applying finger pressure, to anon-conducting surface to provide protection against static chargegeneration. The resistivity of this tape was determined to be about4.5×10¹⁰ ohms/square at 19 percent relative humidity. A control film ofthe release coating, prepared using RDS Bar Coater No. 3 and cured at90° for five minutes, had a resistivity of greater than 10¹³ ohms/squareat 19 percent relative humidity, and a control film of the pressuresensitive adhesive, prepared using RDS Bar Coater No. 8 and cured at 90°for ten minutes, had a resistivity of greater than 10¹³ ohms/square at19 percent relative humidity. The polyester substrate also had aresistivity of greater than 10¹³ ohms/square at this relative humidity.

EXAMPLE 14

A substrate-supported conductive film overcoated with a pressuresensitive adhesive was prepared.

The substrate-supported conductive polymeric film was prepared exactlyas described in the EXAMPLE 12. This composite was overcoated with apressure sensitive adhesive (i.e., a water-based acrylate) (using RDSBar Coater No. 8) to give a conductive composite. The surfaceresistivity, measured on the adhesive side, was 4.8×10⁹ ohms/square at58 percent relative humidity and 2.2×10¹⁰ ohms/square at 9 percentrelative humidity.

EXAMPLE 15

Samples 41 to 50 demonstrate the capability of constructing compositepolymeric films having a substrate, a conductive polymeric film, and anovercoating of an abrasion resistant polymeric film wherein thethicknesses of the films of the composite may be the same or different.

A base coating formulation, that on curing yielded a conductivepolymeric film, was prepared as detailed in EXAMPLE 1, sample 1. Theproportions of A to B in the samples were as specified in TABLE VI.Hydrolyzate solution A (see EXAMPLE 1) was a 67 percent solution, andsilanol-sulfonic acid solution B (see EXAMPLE 1) was a 23 percentsolution.

An overcoating formulation that on curing yielded an abrasion resistantpolymeric film (ARC, see footnote e, Table VI) was prepared according tothe method of EXAMPLE 1 by adding to 6 g of A 4 ml of methanol, a fewdrops of hexafluoroantimonic acid hexahydrate as the acid catalyst, anda few drops of a 10 percent ethyl acetate solution of a fluorochemicalacrylate copolymer (see Ex. 1, U.S. Pat. No. 3,787,351) as the levelingagent.

A polyvinylidene chloride-primed polyethylene terephthalate substratewas coated with the above base coating formulation. The coated substratewas cured at 90° for 30 minutes, and after equilibration of the filmunder ambient conditions for the appropriate period of time, the filmwas overcoated with the overcoating formulation designated in Table VIwith RDS Bar Coater No. 14, unless otherwise specified. The overcoatedmaterial was then cured at 90° for 30 minutes. Both the conductivity andthe haze measurements on these composite films were measured andrecorded in Table VI.

                                      TABLE VI                                    __________________________________________________________________________    Resistivity and Abrasion Resistance of Composite Polymeric Films              Coating formulation                                                                         Composite polymeric film                                            Base Over-                                                                              Surface       Abrasion resistance                               Sample                                                                            coating.sup.a                                                                      coating.sup.b                                                                      Resistivity                                                                            Percent                                                                            (percent haze)                                    no. (A:B)                                                                              (A:B)                                                                              (ohms/square)                                                                          R.H. Before                                                                             After.sup.c                                  __________________________________________________________________________    .sup. 41.sup.e                                                                    3:5  none 2.8 × 10.sup.7                                                                   33   0.6  54.4                                         .sup. 42.sup.e                                                                    3:12 none 7.6 × 10.sup.7                                                                   25   1.3  79.1                                         .sup. 43.sup.e                                                                    3:21 none 3.0 × 10.sup.7                                                                   25   1.0  78.3                                         44  3:5  3:1.sup.a                                                                          2.9 × 10.sup.7                                                                   28   0.4  20.9                                         45  3:12 3:1.sup.a                                                                          2.0 × 10.sup.7                                                                   25   0.6  19.9                                         46  3:21 3:1.sup.a                                                                          2.0 × 10.sup.7                                                                   25   0.9  20.2                                         .sup. 47.sup.e                                                                    None ARC.sup.d                                                                          greater than 10.sup.13                                                                 33   0.4  9.6                                          48  3:5  ARC  3.0 × 10.sup.8                                                                   33   0.4  5.8                                          49  3:15 ARC  .sup. 2.5 × 10.sup.10                                                            25   0.3  4.0                                                        .sup. 2.0 × 10.sup.11                                                             9                                                     50  3:21 ARC  .sup. 1.6 ×  10.sup.10                                                           25   0.5  5.2                                                        .sup. 2.0 × 10.sup.11                                                             9                                                     __________________________________________________________________________     .sup.a A:B represents ratio of A to B as prepared in EXAMPLE 1                .sup.b RDS Bar Coater No. 3 used for overcoating in samples 47 and 48         .sup.c percent haze is measured on a Gardner hazemeter after 1000 cubic       centimeters of falling sand. Low haze value indicated higher abrasion         resistance                                                                    .sup.d Preparation and curing of ARC (abrasion resistant polymeric film)      is described in text for samples 47 to 50                                     .sup.e control                                                           

EXAMPLE 16

A composite composition having a gelatin-containing overcoatingcomposition was prepared.

A polyvinylidene chloride-primed polyethylene terephthalate substratewas coated with a composition prepared as described in sample 2 ofEXAMPLE 1 and cured under the described conditions. The resultantconductive polymeric film was overcoated with a 5 percent aqueousgelatin solution using RDS Bar Coater No. 36. The overcoating was curedby allowing it to stand for one day at room temperature. The resultingcomposite had a surface resistivity of 4.0×10⁸ ohms/square at 61 percentrelative humidity, and 8.8×10¹⁰ ohms/square at 9 percent relativehumidity, while a control sample prepared by coating the gelatin layeron the above uncoated substrate had a surface resistivity of greaterthan 10¹³ ohms/square at 53 percent relative humidity.

EXAMPLE 17

Composite compositions having a fabric substrate were prepared. Samplesof two commercially available fabrics (e.g., woven acrylic and nylontaffeta) were immersed in a vessel containing 1 percent (solids) ofmixtures of A and B (i.e., 3:1 and 3:4 ratios, see EXAMPLE 1) preparedaccording to the directions of EXAMPLE 1. These coated fabric sampleswere then squeezed between two rollers to remove excess coatingcomposition and cured by heating at 90° for ten minutes. Static decaytests of the treated fabrics were then performed, as described inEXAMPLE 1, at 22° and 50 percent relative humidity. The resultsindicated that treated fabrics "bled off" electrostatic charges sincethey had a static decay value of fractions of a second, whereas, thecontrol samples of untreated fabric had static decay values greater thanone second.

EXAMPLE 18

Use of silanol-sulfonate-containing polymeric films of this invention asantifogging films was demonstrated.

A coating formulation prepared according to the directions for sample 1of EXAMPLE 1 was coated onto polyethylene terephthalate using RDS BarCoater No. 22 and cured at 90° for 30 minutes. The remaining uncoatedside of the substrate was similarly coated with the same formulationwhich was then cured as above. The composite film just prepared and acontrol of polyethylene terephthalate film were placed in a freezer at-15° C. for ten minutes. Upon removal of the films from the freezer intoa room at 24° C. and 58 percent relative humidity, the composite filmdid not fog, while the control film did fog. Similarly, when breathedupon, the composite film did not fog, while the control fogged.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodiment setforth herein.

We claim:
 1. A coating composition comprising 1 to 95 weight percent of a hydrolyzate of a hydroxyorganosilane and 5 to 99 weight percent of an aqueous solvent, said hydroxyorganosilane having the general formula:

    R.sup.1 --Si(OR.sup.2).sub.3

wherein R¹ is a di-hydroxy- or polyhydroxy-substituted organic group selected from: (a) alkyl groups containing from 2 to about 8 carbon atoms and substituted by 2 to 7 hydroxy groups, with any single carbon atom having at most one hydroxy group attached; (b) alkyl groups and cyclic alkyl groups having 2 to 20 carbon atoms, which carbon chain may be interrupted by one or more oxygen atoms and containing at least two hydroxyl groups per 8 carbon atoms with any single carbon atom having at most one hydroxy group attached; (c) aralkyl or alkaryl groups containing 7 to 10 carbon atoms, said aralkyl or alkaryl group having 2 to 8 hydroxy groups, with any single carbon atom having at most one hydroxy group attached; (d) alkenyl groups containing 4 to 8 carbon atoms and 2 to 5 hydroxy groups with any single carbon atom having at most one hydroxy group attached; (e) cyclic or alkyl-substituted cyclic groups having 3 to 8 carbon atoms and substituted by 2 to 7 hydroxy groups, with any single carbon atom having at most one hydroxy group attached; andR² is selected from: (a) hydrogen, and (b) any organic group such that the --Si(OR²)₃ moiety is hydrolyzable.
 2. A coating composition comprising:(1) 1 to 95 weight percent of a hydrolyzate of a hydroxyorganosilane and 5 to 99 weight percent of an aqueous solvent, said hydroxyorganosilane having the general formula:

    R.sup.1 --Si(OR.sup.2).sub.3

wherein R¹ is a hydroxy or polyhydroxy-substituted organic group selected from:(a) alkyl groups containing from about 2 to about 8 carbon atoms and substituted by 1 to 7 hydroxy groups, with any single carbon atom having at most one hydroxy group attached; (b) alkyl groups and cyclic alkyl groups having up to 20 carbon atoms, which carbon chain may be interrupted by one or more oxygen atoms and containing at least one hydroxyl group per 8 carbon atoms with any single carbon atom having at most one hydroxy group attached; (c) aralkyl or alkaryl groups containing 7 to 10 carbon atoms, said aralkyl or alkaryl group having 1 to 8 hydroxy groups, with a single carbon atom having at most one hydroxy group attached; (d) alkenyl groups containing up to 8 carbon atoms and 1 to 5 hydroxy groups with any single carbon atom having at most one hydroxy group attached; (e) cyclic or alkyl-substituted cyclic groups having 3 to 8 carbon atoms and substituted by 1 to 7 hydroxy groups, with any single carbon atom having at most one hydroxy group attached; and R² is selected from:(a) hydrogen, and (b) any organic group such that the Si(OR²)₃ moiety is hydrolyzable; and (2) in the range of 0.001 to 50 weight percent of a silanol-sulfonate compound having the general formula: ##STR13## wherein Q is selected from hydroxyl, alkyl groups containing from 1 to about 4 carbon atoms and alkoxy groups containing from 1 to about 4 carbon atoms; X is an organic linking group containing up to 10 carbon atoms; Y is an organic or inorganic cation; r is equal to the valence of Y; and n is 1 or 2,with the proviso that the mole ratio of silanol-sulfonate compound to organosilane is less than 5 to
 1. 3. The coating composition according to claims 1 or 2 wherein R¹ is selected from (1) a hydroxyalkyl group having 2 to 4 carbon atoms, and (2) a dihydroxy-substituted alkyl group having 4 to 8 carbon atoms whose chain may be interrupted by 1 or 2 oxygen atoms.
 4. The coating composition according to claim 2 wherein said hydroxyorganosilane or precursor is selected from the group consisting of: ##STR14##
 5. The coating composition according to claims 1 or 2 wherein R² is selected from the group containing straight chain or branched alkyl, alkaryl, acyl, and aroyl groups having up to 8 carbon atoms.
 6. The coating composition according to claim 2 wherein X is selected from alkylene, hydroxy-substituted alkylene, and mono-oxa alkylene groups having at least two or more methylene groups; cycloalkylene groups; alkyl-substituted cycloalkylene groups; hydroxy-substituted alkylene groups; hydroxy-substituted mono-oxa alkylene groups; divalent hydrocarbon groups having mono- or poly-oxa backbone substitution; divalent hydrocarbon groups having mono-thia backbone substitution; divalent hydrocarbon groups having mono-thia backbone substitution; divalent hydrocarbon groups having mono-oxa-thia backbone substitution; divalent hydrocarbon groups having dioxo-thia backbone substitution; arylene groups; arylalkylene groups; alkylarylene groups; substituted alkylarylene groups; and alkylarylalkylene groups.
 7. The coating composition according to claim 2 wherein Y is selected from the class consisting of hydrogen, alkali metals, aklaline earth metals, transition metals, heavy metals, organic cations of protonated weak bases having an average molecular weight of less than 400 and a pK_(a) of less than 11, and organic cations of strong organic basis having an average molecular weight of less than 400 and a pK_(a) of greater than
 11. 8. The coating composition according to claim 2 wherein said sulfonate moiety is replaced by a phosphonate moiety.
 9. The coating composition according to claim 2 wherein said silanol-sulfonate compound is replaced by a monomeric or polymeric alkyl-, aryl-, alkaryl-, and aralkyl-sulfonic acid, or salt thereof, having up to 20 carbon atoms per sulfonic acid group.
 10. The coating composition according to claim 7 wherein said silanol-sulfonate is selected from the group of compounds having the formulae ##STR15## wherein Q' is an alkyl group having 1 to 4 carbon atoms and X is an organic linking group containing up to 10 carbon atoms.
 11. The coating composition according to claim 10 wherein said silanol-sulfonate is selected from the group of compounds consisting of ##STR16##
 12. The coating composition according to claims 1 or 3 further comprising 1 to 5 weight percent of the total reactive monomers of an acid catalyst.
 13. The coating composition according to claim 12 wherein said acid catalyst is hexafluoroantimonic acid hexahydrate.
 14. The coating composition according to claim 12 wherein said acid catalyst is a photoactivatable initiator.
 15. The coating composition according to claims 1 or 3 further comprising 0.001 to 95 weight percent of additives selected from viscosity modifiers, hardness modifiers, pigments, fillers, UV absorbers, colorants, and leveling agents.
 16. The coating composition according to claim 15 wherein said additives further comprise at least one of co-reactive organosilane monomers, oligomers, and polymers.
 17. The coating composition according to claim 16 wherein said organosilane monomer or oligomer is selected from methylsilanetriol and oligomers, orthosilicates, and hydroxyorganosilanes having the formula: ##STR17## wherein R¹ and R² are defined above;R³ is a lower alkyl group having 1 to 4 carbon atoms or phenyl; a=2 or 3; b=1 or 2;with the proviso that (a+b) is equal to 3 or
 4. 18. The cured polymeric product according to claim 1 cured in situ by at least one curing source selected from heat and radiation.
 19. The cured polymeric product of claims 1 or
 2. 